WO2010072762A1

WO2010072762A1 - Composition based on natural rubber and a reinforcing inorganic filler comprising a dihydrazide

Info

Publication number: WO2010072762A1
Application number: PCT/EP2009/067749
Authority: WO
Inventors: Julien Thuilliez; Stéphanie DE LANDTSHEER; Brigitte Chauvin
Original assignee: Societe De Technologie Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2008-12-23
Filing date: 2009-12-22
Publication date: 2010-07-01
Also published as: JP5752604B2; FR2940298A1; EP2382264A1; CN102257056A; US20120270966A1; JP2012513517A; FR2940298B1

Abstract

Reinforced rubber composition based on at least: (a) an elastomeric matrix predominantly based on natural rubber; (b) a reinforcing filler predominantly based on an inorganic filler; (c) a coupling agent; and (d) a dihydrazide compound satisfying the following formula (I), in which R is a divalent hydrocarbon radical chosen from aromatic radicals having 6 to 20 carbon atoms and saturated or unsaturated aliphatic radicals having 2 to 20 carbon atoms; and n is equal to 0 or 1. This rubber composition is intended for example for the manufacture of a semi-finished rubber product for making motor vehicle tyres.

Description

COMPOSITION BASED ON NATURAL RUBBER AND INORGANIC REINFORCING LOAD COMPRISING DIHYDRAZIDE

The present invention relates to reinforced rubber compositions based on natural rubber of which more than half of the reinforcing filler is inorganic. These rubber compositions are intended for example for the manufacture of a semi-finished rubber product intended for the tire of motor vehicles.

It is known that, in general, in order to obtain the optimum reinforcement properties conferred by a filler, the filler should be present in the elastomeric matrix in a final form which is at once as finely divided as possible and distributed in the as homogeneous as possible. However, such conditions can be achieved only to the extent that the load has a very good ability, on the one hand to incorporate into the matrix during mixing with the elastomer and to deagglomerate, on the other hand to to disperse homogeneously in this matrix. As is well known, carbon black has such abilities. However, since fuel economy and the need to protect the environment have become a priority, it has been necessary to produce tires with reduced rolling resistance without penalizing their wear resistance. This has been made possible in particular by the use, in the rubber compositions, of specific inorganic fillers, capable of competing with the reinforcing point of view with a conventional pneumatic grade carbon black, while offering these compositions a higher hysteresis. low, synonymous with lower rolling resistance for tires with them. Further reducing the rolling resistance remains in the current economic and ecological context a permanent concern despite the low levels reached with the specific inorganic fillers described as "reinforcing". Many tracks have already been explored to further lower the hysteresis of rubber compositions reinforced with such fillers. By way of example, mention may be made of modifying the structure of diene polymers at the end of polymerization by means of functionalising, coupling or starring agents in order to obtain a good interaction between the polymer thus modified. and the reinforcing inorganic filler. The inventors have discovered during their research that in a composition of rubber based on natural rubber as the main elastomer and reinforced with an inorganic filler in a majority, the use of certain dihydrazide compounds allows to significantly reduce the hysteresis of the composition. This decrease in hysteresis in the proportions observed is, to say the least, unexpected. Indeed, hydrazides are generally known to lower the hysteresis of natural rubber-based mixtures containing carbon black as a single or majority reinforcing filler. For example, EP 0 738 754 A1 illustrate hybrid mixtures containing carbon black as a majority feed whose decrease in hysteretic losses is of the order of 8% after addition of dihydrazide compounds.

When an inorganic filler is used as the sole or majority reinforcing filler, relatively low hysteresis levels are already achieved. However, the inventors have demonstrated that the addition of a dihydrazide compound to a mixture based on natural rubber loaded with silica, not only allowed to lower the hysteresis level of this mixture, but also to lower it. in significant and unexpected proportions, much higher than those observed in the prior art for hybrid mixtures containing carbon black as majority reinforcing filler.

Given the significantly improved hysteretic properties of this composition based on natural rubber reinforced with an inorganic filler, the latter is particularly suitable for the manufacture of semi-finished rubber products for motor vehicle tires.

Thus, an object of the present invention is a reinforced rubber composition based at least on an elastomeric matrix comprising natural rubber, a reinforcing filler comprising an inorganic filler in a weight fraction of more than 50% by weight. total of the charge, a coupling agent and a dihydrazide compound corresponding to the following formula I:

O O

H ₂ NHNC - R _n - CNHNH ₂ Formula I wherein R is a divalent hydrocarbon radical selected from aromatic radicals, substituted or not, having 6 to 20 carbon atoms, aliphatic, saturated or unsaturated, linear or branched, having 2 and 20 carbon atoms and n is 0 or 1. Another object of the invention is a method for preparing such a reinforced rubber composition defined above.

The invention also relates to a semi-finished tire rubber product consisting wholly or partly of the reinforced rubber composition defined above. Another object of the invention is a tire comprising at least one semi-finished rubber product consisting wholly or partly of the reinforced rubber composition as defined above.

For clarity on reading the following, the expression "composition based on" means a composition comprising the mixture and / or the reaction product of the various constituents used, some of these basic constituents being capable of or intended to react with one another at least in part during the various phases of manufacture of the composition, in particular during its crosslinking or vulcanization. In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are% by weight. On the other hand, any range of values designated by the expression "between a and b" represents the range of values from more than a to less than b (i.e. terminals a and b excluded) while any range of values designated by the term "from a to b" means the range from a to b (i.e., including the strict limits a and b). Moreover, the amounts of the components of the invention can be expressed in phr, that is to say in part (by weight) per hundred parts by weight of elastomer.

Thus, a first object of the invention is a reinforced rubber composition based at least on (a) an elastomeric matrix comprising at least natural rubber, (b) a reinforcing filler consisting of more than 50% by weight of d an inorganic filler, (c) a coupling agent and (d) a dihydrazide compound having the following formula I: OO

H ₂ NHNC - R _n - CNHNH ₂

Formula I in which R is a divalent hydrocarbon radical chosen from aromatic radicals, substituted or unsubstituted, having 6 to 20 carbon atoms, linear or branched, saturated or unsaturated aliphatic radicals having 2 and 20 carbon atoms and n is 0 or 1.

The dihydrazide compounds are compounds described in the state of the art essentially to reduce the self-heating of rubber compositions. Examples include EP 0 478 274 A1. The dihydrazide compounds have also been used in rubber compositions for the production of tread, in combination with various other compounds. Thus, for example, EP 1 083 199 A1 discloses a tread composition comprising a dihydrazide compound in the presence of a bismaleimide to mitigate the negative effects of the latter on the properties of the rubber composition which contains it. EP 0 761 733 A1 associates isophthalic dihydrazide with specific carbon blacks and functionalized SBRs in - AT -

tread compositions. Al combines the isophthalic dihydrazide and the isonicotinic dihydrazide with a functionalized butyl polymer in a natural rubber tread composition.

According to the present invention, the dihydrazide compounds corresponding to formula I are preferably chosen from those for which, in formula I, R is a divalent hydrocarbon radical chosen from unsubstituted aromatic radicals having 6 to 14 carbon atoms, aliphatic radicals linear saturates having 3 to 12 carbon atoms

More preferentially, these dihydrazide compounds are chosen from phthalic dihydrazide, isophthalic dihydrazide, terephthalic dihydrazide, succinic dihydrazide, adipic dihydrazide, azeic dihydrazide, sebacic dihydrazide, oxalic dihydrazide and dodecanoic dihydrazide.

The rubber composition of the tire component according to the invention comprises the dihydrazide compound in an amount ranging from 0.25 to 7 phr, preferably from 0.3 to 2.5 phr and more preferably from 0.5 to 2 phr. By "dihydrazide compound" according to the invention is meant a compound or a mixture of several compounds of formula I. The rubber composition according to the invention comprises at least four compounds, including an elastomeric matrix.

According to the invention, the elastomeric matrix of the composition is based on natural rubber. In some cases, the elastomeric matrix may advantageously consist entirely of natural rubber (100% of the elastomeric matrix is made of natural rubber). This variant is preferably implemented when it comes to using the rubber composition to manufacture tire treads of commercial vehicles such as heavy goods vehicles or certain applications, such as ice or snow, vehicle tourism, or to manufacture metal / rubber reinforcing composites, such as, for example, crown or carcass plies. The elastomeric matrix may also, in addition to the natural rubber, comprise at least one other diene elastomer.

This or these other diene elastomers are then present in the matrix in proportions of between 0 and 50% by weight (the boundaries of this domain being excluded), preferably between 5% and 40%, for example from 15% to 35%. In the case of a blend with at least one other diene elastomer, the weight fraction of the natural rubber in the elastomeric matrix is predominant and preferably greater than or equal to 50% by weight of the total weight of the matrix, still more preferably between 60 % and 95%, for example from 65% to 85% by weight of the total weight of the matrix. The majority weight fraction according to the invention is the highest weight fraction of the blend. Thus, in a NR / elastomer A / elastomer B blend, the weight fractions can be divided into 40/40/20 or 40/30/30, the majority weight fractions being 40. And in an NR / elastomer blend, the weight fractions are can be divided into 50/50 or 70/30, the majority weight fractions being 50 or 70.

By diene elastomer, it is to be understood according to the invention any functionalized natural rubber or any synthetic elastomer derived at least in part from diene monomers. More particularly, diene elastomer is any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms, or any copolymer obtained by copolymerization of one or more conjugated dienes with one another or with one or more vinylaromatic compounds. having from 8 to 20 carbon atoms. In the case of copolymers, these contain from 20% to 99% by weight of diene units, and from 1 to 80% by weight of vinylaromatic units. The functionalized natural rubber according to the invention is preferably an epoxidized natural rubber (ENR). The diene elastomer constituting a part of the elastomeric matrix according to the invention is preferably chosen from the group of highly unsaturated diene elastomers consisting of polybutadienes (BR), butadiene copolymers, polyisoprenes (PI) and isoprene copolymers. and mixtures of these elastomers. Such copolymers are more preferably selected from the group consisting of copolymers of butadiene and a vinylaromatic monomer, more particularly butadiene-styrene copolymer (SBR), isoprene-butadiene copolymers (BIR), copolymers of isoprene and a vinylaromatic monomer, more particularly the isoprene-styrene copolymer (SIR) and the isoprene-butadiene-styrene copolymers (SBIR). Of these copolymers, copolymers of butadiene and a vinylaromatic monomer, more particularly the butadiene-styrene copolymer (SBR), are particularly preferred.

The diene elastomer constituting a part of the elastomeric matrix according to the invention may be star, coupled, functionalized or otherwise, in a manner known per se, by means of functionalising, coupling or staring agents known to man. Of the more conventional art, the elastomers coupled according to the methods described in the applications in the name of the Applicants WO 08/141702, FR 2 2910 64, FR 2 291 065 and FR 07/60442 can for example be cited more among the more conventional ones. .

The rubber composition according to the invention comprises at least four compounds, including a reinforcing filler in proportions ranging from 35 to 200 phr. Preferably, the total reinforcing filler content is between 40 and 140 phr, more preferably between 50 and 130 phr, the optimum being in a known manner different according to the particular applications of the invention. targeted pneumatic; the level of reinforcement expected on a bicycle tire, for example, is of course less than that required on a tire capable of running at high speed in a sustained manner, for example a motorcycle tire, a tire for a passenger vehicle or for a commercial vehicle such as than heavy weight. According to the invention, the reinforcing filler is mainly constituted by a reinforcing inorganic filler, that is to say that the proportion of inorganic filler is greater than or equal to 50% by weight of the total weight of the filler, more particularly higher at 50%, up to a maximum of 100%. Preferably, the reinforcing filler consists of 55 to 95% by weight of an inorganic filler. By "reinforcing inorganic filler" is meant in the present application, by definition, any inorganic or mineral filler regardless of its color and origin (natural or synthetic), also called "white" charge, "clear" charge or "non-black filler", as opposed to carbon black, capable of reinforcing on its own, without any other means than an intermediate coupling agent, a rubber composition intended for the manufacture of tires, in other words capable of replacing, in its reinforcing function, a conventional carbon black of pneumatic grade; such a filler is generally characterized, in known manner, by the presence of hydroxyl groups (-OH) on its surface.

Preferably, the reinforcing inorganic filler is, wholly or at least predominantly, silica (SiO ₂ ). The silica used may be any reinforcing silica known to those skilled in the art, in particular any precipitated or fumed silica having a BET surface and a CTAB specific surface area both less than 450 m ² / g, even if the highly dispersible precipitated silicas are preferred. As reinforcing inorganic filler, mention may also be made of mineral fillers of the aluminous type, in particular alumina (Al 2 O 3) or aluminum (oxide) hydroxides, or reinforcing titanium oxides. The physical state under which the reinforcing inorganic filler is present is indifferent, whether in the form of powder, microbeads, granules or beads. Of course, reinforcing inorganic filler is also understood to mean mixtures of different reinforcing inorganic fillers, in particular of highly dispersible silicas as described above. It will be noted that the reinforcing filler may contain, in addition to the abovementioned reinforcing inorganic filler (s), an organic filler, such as carbon black. This reinforcing organic filler is then preferably present in a weight fraction of less than 50% relative to the total weight of the filler.

Suitable carbon blacks are all carbon blacks, especially blacks of the HAF, ISAF, SAF, FF, FEF, GPF and SRF type conventionally used in surfactant compositions. tire rubber (so-called pneumatic grade black). Among these, the reinforcing carbon blacks of the 100, 200 or 300 series (ASTM grades), for example the Nl 15, N134, N234, N326, N330, N339, N347 and N375 blacks, but also coarser blacks such as blacks N550 or N683. Carbon blacks could for example already be incorporated into natural rubber in the form of a masterbatch.

For example, black / silica or partially or fully silica-coated blacks are suitable for forming the reinforcing filler. Also suitable are silica-modified carbon blacks, such as, without limitation, the charges which are sold by CABOT under the name "CRX 2000", and which are described in the international patent document WO-A- 96/37547.

As examples of organic fillers other than carbon blacks, mention may be made of the organic functionalized polyvinylaromatic fillers as described in applications WO-A-2006/069792 and WO-A-2006/069793, or else the organic fillers of polyvinyl non-aromatic functionalized as described in applications WO-A-2008/003434 and WO-A-2008/003435.

In the case where the reinforcing filler contains only a reinforcing inorganic filler and carbon black, the weight fraction of this carbon black in said reinforcing filler is more preferably chosen less than or equal to 30% relative to the total weight of the reinforcing filler. The rubber composition according to the invention comprises at least four compounds, including a coupling agent for coupling the reinforcing inorganic filler to the natural rubber and to any diene elastomers that make up the elastomeric matrix.

By coupling agent is more specifically meant an agent capable of establishing a sufficient chemical and / or physical bond between the charge in question and the elastomer, while facilitating the dispersion of this charge within the elastomeric matrix. Such a binding agent, at least bifunctional, has for example as simplified general formula "Y-T-X", in which:

Y represents a functional group ("Y" function) which is capable of binding physically and / or chemically to the inorganic filler, such a bond possibly being established, for example, between a silicon atom of the coupling agent and the hydroxyl (-OH) groups of the surface of the inorganic filler (for example the surface silanols when it is silica);

X 'represents a functional group ("X""function) capable of bonding physically and / or chemically to the elastomer, for example via a sulfur atom; • T represents a divalent group making it possible to connect Y and X '.

The bonding agents should not be confused with simple charge-covering agents considered which, in a known manner, may have the active Y function with respect to the charge but lack the function X 'active vis-à-vis the charge. with respect to the elastomer. Any binding agent known for, or capable of effectively ensuring, in the tire rubber compositions used for the manufacture of tires, the bonding (or coupling) between an inorganic reinforcing filler such as silica and a diene elastomer, may be used. as for example organosilanes, in particular polysulfurized alkoxysilanes or mercaptosilanes, or else polyorganosiloxanes carrying the aforementioned X 'and Y functions. Silica / elastomer bonding agents, in particular, have been described in a large number of documents, the best known of which are bifunctional alkoxysilanes such as polysulfurized alkoxysilanes. In particular, polysulfide silanes, called "symmetrical" or "asymmetrical" silanes according to their particular structure, are used, as described for example in the applications WO03 / 002648 (or US 2005/016651) and WO03 / 002649 (or US 2005/016650). As examples of polysulfurized silanes, mention may be made more particularly of polysulfides of bis (3-trimethoxysilylpropyl) or of bis (3-triethoxysilylpropyl). Among these compounds, bis (3-triethoxysilylpropyl) tetrasulfide, abbreviated as TESPT, or bis (triethoxysilylpropyl) disulfide, abbreviated as TESPD, is especially used. Mention may also be made, by way of preferred examples, of polysulfides (in particular disulphides, trisulphides or tetrasulfides) of bis- (monoalkoxyl (Cl-C4) -dialkyl (Cl-C4) silylpropyl), more particularly bis-monoethoxydimethylsilylpropyl tetrasulfide, as described above. in the patent application WO 02/083782 (or US 2004/132880).

As coupling agent other than polysulfurized alkoxysilane, mention may be made in particular of bifunctional POSS (polyorganosiloxanes) or polysulfides of hydroxysilane as described in patent applications WO 02/30939 (or US Pat. No. 6,774,255) and WO 02 / 31041 (or US 2004/051210), or silanes or POSS carrying azodicarbonyl functional groups, as described for example in patent applications WO 2006/125532, WO 2006/125533, WO 2006/125534. In the compositions according to the invention, the level of coupling agent is advantageously less than 20 phr, it being understood that it is generally desirable to use as little as possible. Its level is preferably between 0.5 and 12 phr, more preferably from 3 to 10 phr, in particular from 4 to 7 phr. This level is easily adjusted by those skilled in the art according to the level of inorganic filler used in the composition. Those skilled in the art will understand that, as the equivalent filler of the reinforcing inorganic filler described in this paragraph, it would be possible to use a reinforcing filler of another nature, in particular an organic filler, since this reinforcing filler would be covered with a filler. inorganic layer such as silica, or would comprise on its surface functional sites, especially hydroxyl, requiring the use of a coupling agent to establish the bond between the filler and the elastomer.

The rubber compositions in accordance with the invention may also contain, in addition to the coupling agents, coupling activators, inorganic charge-covering agents or, more generally, processing aid agents which may be used in a known manner, by improving the dispersion of the filler in the rubber matrix and lowering the viscosity of the compositions, to improve their ability to implement in the green state, these agents being for example hydrolysable silanes such as alkylalkoxysilanes, polyols, polyethers, primary, secondary or tertiary amines, hydroxyl or hydrolysable polyorganosiloxanes. The rubber compositions in accordance with the invention may also comprise all or part of the usual additives normally used in elastomer compositions intended for the manufacture of tires, for example pigments, protective agents such as anti-ozone waxes, chemical antiozonants, anti-oxidants, anti-fatigue agents, reinforcing or plasticizing resins, acceptors (for example phenolic novolak resin) or methylene donors (for example HMT or H3M) as described, for example, in the application WO 02/10269, a crosslinking system based on either sulfur, or sulfur and / or peroxide donors and / or bismaleimides, vulcanization accelerators, vulcanization activators, adhesion promoters such as compounds based on cobalt, plasticizing agents, preferably non-aromatic or very weakly aromatic selected from the group consisting of nonpolar liquid stabilizers such as naphthenic oils, paraffinic oils, MES oils, TDAE oils, polar liquid plasticizers such as ethers and esters plasticizers (for example glycerol trioleate and more particularly oleic sunflower oil), and resins solid hydrocarbon compounds having a high Tg, preferably greater than 30 ^° C., as described, for example, in the applications WO 2005/087859, WO 2006/061064 and WO 2007/017060, and the mixtures of such compounds.

The invention also relates to a method for preparing a rubber composition as described above. It should be noted that, according to the invention, the dihydrazide compound can be incorporated at any time in the process for the preparation of the rubber composition described above, including during the manufacture of natural rubber at its production site. The composition is manufactured in appropriate mixers, using two successive preparation phases well known to those skilled in the art: a first phase of work or thermomechanical mixing (so-called "non-productive" phase) at high temperature, up to a maximum of maximum temperature between 110 ⁰ C and 190 ⁰ C, preferably between 130 ⁰ C and 180 ⁰ C, followed by a second phase of mechanical work (so-called "productive" phase) to a lower temperature, typically less than 110 ⁰ C, for example between 40 ⁰ C and 100 ⁰ C, finishing phase during which is incorporated the crosslinking system.

The process according to the invention for preparing a rubber composition according to the invention comprises at least the following steps:

The production, at a maximum temperature of between 130 ^° C. and 200 ^° C., preferably between 145 ° C. and 185 ° C., of a first thermomechanical working time (sometimes referred to as a "non-productive" phase) of the constituents of basis of the rubber composition, with the exception of the crosslinking system and optionally an adhesion promoter, by intimately incorporating, by kneading into one or more steps, the elastomer matrix based on natural rubber, ingredients of the composition, then

The production, at a temperature below said maximum temperature of said first time, preferably below 120 ^° C., of a second mechanical working time during which said crosslinking system is incorporated and, if appropriate, an adhesion promoter; . The final composition thus obtained can then be calendered, for example in the form of a sheet, a plate or extruded, for example to form a rubber profile usable as a semi-finished rubber product for the tire. ... The dihydrazide compound of formula I described above can be incorporated

• as an additive in the manufacture of natural rubber at its production site,

Or as an ingredient of the rubber composition according to the invention: during the prior embodiment of a natural rubber / dihydrazide masterbatch on an open tool of the cylinder-tool type or on a closed tool of the internal mixer type, without prior embodiment of a masterbatch, directly into the mixer during the first non productive phase with the other compounds of the rubber composition. Therefore, a variant of the process according to the invention comprises, prior to carrying out step (i) above, the steps of the conventional manufacture of natural rubber which comprises the addition of the dihydrazide compound of formula I.

Another variant of the process according to the invention comprises, prior to carrying out step (i) above, a step of preparing a masterbatch based on natural rubber and the dihydrazide compound of formula I.

According to another variant of the process of the invention, all the basic constituents of the composition of the invention, including the dihydrazide compound but with the exception of the vulcanization system, are incorporated during the first step (i). , so-called non-productive phase. The invention also relates to a tire which incorporates in at least one of its constituent elements a reinforced rubber composition according to the invention.

The invention particularly relates to a semi-finished rubber product comprising a reinforced rubber composition according to the invention for these tires. Because of the reduced hysteresis which characterizes a reinforced rubber composition according to the invention, it will be noted that a tire whose tread comprises the composition has a rolling resistance advantageously reduced.

Because of the reduced hysteresis which characterizes a reinforced rubber composition according to the invention, it will also be noted that a tire of which all or part of the internal compositions comprise the composition of the invention has a significantly reduced self-heating, and therefore improved endurance By internal compositions are meant the compositions in contact with the reinforcements and textile or metal reinforcements of the tire and the compositions which are adjacent to them in the tire, apart from any composition in contact with the air or an inflation gas. The tires in accordance with the invention are intended in particular for passenger vehicles as well as for industrial vehicles chosen from vans, "heavy goods vehicles" - ie, metro, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles. road, agricultural or civil engineering machinery, airplanes, other transport or handling vehicles. The aforementioned features of the present invention, as well as others, will be better understood on reading the following description of several embodiments of the invention, given by way of illustration and not limitation.

• MEASUREMENTS AND TESTS USED The rubber compositions are characterized before and after firing, as indicated below: a) Mooney viscosity ML (1 + 4) at 100 ° C: measured according to ASTM standard D-1646, entitled

"Mooney" in the tables, an increase in relative value represents an increase in Mooney viscosity.

(b) hardness SHORE A: measurements made according to DIN 53505, an increase in the relative value represents an increase of Shore.

(c) the Scott breaking index at 23 ° C: the breaking stress (FR) in MPa and the elongation at break (AR) in% are determined. All these tensile measurements are carried out under normal conditions of temperature and hygrometry according to ISO 37, an increase in the relative value representing an increase in the stress and an increase in elongation at break.

(d) Delta G * and tan (δ) max dynamic properties are measured on a viscoanalyzer (Metravib VA4000) according to ASTM D 5992-96. The response of a sample of vulcanized composition (cylindrical specimen 2 mm thick and section 79 mm ² ), subjected to sinusoidal stress in alternating simple shear, at the frequency of 10 Hz, under normal conditions is recorded. temperature (23 ° C) according to ASTM D 1349-99. A peak-to-peak deformation amplitude sweep of 0.1 to 50% (forward cycle) followed by 50% to 0.1% (return cycle) is performed. The results exploited are the complex dynamic shear modulus (G *) and the loss factor tan δ. For the return cycle, the maximum value of tan δ observed (tan (δ) max), as well as the complex modulus difference (Delta G *) between the values at 0.1 and 50% of deformation (Payne effect) are indicated. ). An increase in the relative value represents an increase in the measured value.

EXAMPLE 1 Compositions comprising either an elastomer according to the invention or elastomers not in accordance with the invention

Incorporation of the molecule:

Several hydrazide-type molecules have been used as natural rubber additives

terephthalic dihydrazide,

adipic dihydrazide,

- Dodecanoic dihydrazide.

isophthalic dihydrazide - hydroxynaphthoic monohydrazide

blocked hydroxynaphthoic monohydrazide (BMH) Ia monohydrazide propionique monohydrazide benzhydrazide

The molecules are represented in the figures below,

dihydrazide terephthalic dihydrazide adipic dihydrazide dodecanoic

isophthalic dihydrazide HNTH hydrazide 2 hydroxy-3-naphthoic

BMH: N '- [(1Z) -1,3-Dimethylbutylidene] -3-hydroxy-2-naphthohydrazide or 3-Hydroxy-2-naphthylhydrazone

Propionic hydrazide

The method of incorporation of the molecule is as follows:

On a roll tool (roll temperature controlled at 23 ^° C.), the rollers of which have a diameter of 150 mm, a gap of 2 mm and a rotation speed of the rolls of 20 rev.min ^-1 , natural rubber undergoes the following steps:

1) 3 passes of the natural rubber initially at room temperature; 2) adding a given amount of molecule in powder form;

SUBSTITUTE SHEET (RULE 26) 3) making 12 passes so as to disperse the powder and to homogenize the sample.

Two different types of natural rubber have been tested to form the masterbatches, a NR referenced TSR20 and a NR referenced TSR3L.

The detail is shown in Table 1 below. Table 1

The propionic molecules, HNH, BMH and benzhydrazide are counterexamples (aliphatic monohydrazides, benzic or naphthoic and naphthoic blocked). Each of the compositions has the following formulation (expressed in phr: parts per hundred parts of elastomer): Table la

(1) = Natural rubber

(2) = Rhodia Zeosil 1165MP Silica (BET and CTAB: approximately 160 m ² / g) (3) = N330 carbon black

(4) = N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine

(5) = coupling agent TESPT ("Si69" from Degussa)

(6) = CBS (Flexsys Santocure)

Each of the following compositions is carried out initially by thermomechanical work and then, in a second finishing time, by mechanical work. Is introduced successively, in a laboratory internal mixer type 'Banbury', whose capacity is 400 cm ³ , which is filled to 75% and whose initial temperature is about 50 ⁰ C, the elastomer, the black of carbon, 2/3 of the silica and the coupling agent. At 90 ^° C., the last third of the silica, stearic acid, 6PPD and paraffin. Zinc oxide is introduced at 140 ^° C.

The thermomechanical working step is carried out for 3 to 5 minutes, until a maximum temperature of about 165 ° C. falls.

The aforementioned first thermomechanical work time is thus achieved, it being specified that the average speed of the pallets during this first time is 70 rpm. The mixture thus obtained is recovered, cooled and then, in an external mixer (homo-finisher), the sulfur and sulfenamide are added at 30 ^° C., mixing again for a period of 3 to 4 minutes (second time). aforementioned mechanical work).

The compositions thus obtained are then calendered, either in the form of plates (with a thickness ranging from 2 to 3 mm) or thin rubber sheets, for the measurement of their physical or mechanical properties. The compositions thus obtained can also be extruded in the form of directly usable profiles, after cutting and / or assembly to the desired dimensions, for example as semi-finished products for tires.

Table Ib:

It will be noted that the compositions K, L, M and N according to the invention have a Mooney value "mixture" greater than that of the composition A based on a NR that is not modified on the one hand and higher than that of the composition B based on a NR only worked on tool on the other hand. As regards the dynamic properties, it will be noted that the values of Delta G * and tan (δ) max of the compositions K, L, M and N according to the invention are lower than those of the composition A based on an unmodified NR and lower than that of the composition B based on a NR only passed on tool. The elastomers K, L, M and N comprising a terephthalic, isophthalic or aliphatic dihydrazide according to the invention make it possible to improve the hysteretic properties with respect to the unmodified elastomer A and with respect to the elastomer B only passed on a tool without Molecule introduction.

In other words, the compositions K, L, M and N according to the invention based on NR comprising a terephthalic dihydrazide or an isophthalic dihydrazide or an adipic dihydrazide or a dodecanoic hydrazide have rubber properties in the crosslinked state which are improved over those of the unmodified NR composition A due to significantly reduced hysteresis.

Compositions Q, S and T not in accordance with the invention have higher Delta G * values than composition A based on unmodified NR. Compositions Q, S and T not in accordance with the invention have values of tan (δ) max greater than or equivalent to those of composition A based on unmodified NR. The elastomers Q, S and T comprising a hydroxynaphthoic hydrazide or a propionic hydrazide or a benzhydrazide do not make it possible to improve the hysteretic properties with respect to the unmodified elastomer A.

It will be noted that the Delta G * and tan (δ) max values of the composition R not according to the invention are lower than those of the composition A based on an unmodified NR. However, the values of Delta G * and tan (δ) max of the compositions K, L, M and N according to the invention are lower than those of the composition R based on a NR comprising a hydroxy-naphthylhydrazone (BMH). . In other words, compositions K, L, M and N according to the invention have crosslinked rubber properties which are improved over those of BMH-based composition R. Table Ic

It will be noted that the compositions O and P according to the invention have a higher Mooney "mixture" value than that of the composition F based on a NR which is not modified on the one hand and higher than that of the composition G based on a NR only worked on tool on the other hand. As regards the dynamic properties, it will be noted that the values of Delta G * and tan (δ) max of the compositions O and P according to the invention are lower than those of the composition F based on an unmodified NR and that of the composition G based on a NR only passed on tool. The O and P elastomers comprising a terephthalic or adipic dihydrazide according to the invention make it possible to improve the hysteretic properties with respect to the unmodified elastomer F and with respect to the elastomer G only passed on a tool without introducing a molecule. In other words, the compositions O and P according to the invention based on NR comprising a terephthalic dihydrazide or an adipic dihydrazide have crosslinked rubber properties which are improved over those of the composition F based on unmodified NR and composition G based on a NR only worked on tool on the other hand because of a significantly reduced hysteresis.

Example 2

BINARY CUTTING OF ELASTOMERES

Each of these compositions has the following formulation (expressed in phr: parts per hundred parts of elastomer): Table 2a

(1) = Natural rubber

(2) = SSBR with 26% styrene and 24% 1,2 polybutadiene units

(3) = Rhodia Zeosil 1165MP Silica (BET and CTAB: approximately 160 m ² / g) (4) = N330 carbon black

(5) = N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine

(6) = coupling agent TESPT ("Si69" from Degussa)

(7) = CBS (Flexsys Santocure) Each of the following compositions is carried out, firstly, by thermomechanical work, then, in a second finishing time, by mechanical work. Is introduced successively, in a laboratory internal mixer type 'Banbury', whose capacity is 400 cm ³ , which is filled to 75% and whose initial temperature is about 50 ⁰ C, the elastomer, the black of carbon, 2/3 of the silica and the coupling agent. At 90 ^° C., the last third of the silica, stearic acid, 6PPD and paraffin. Zinc oxide is introduced at 140 ^° C.

The compositions thus obtained are then calendered, either in the form of plates (with a thickness ranging from 2 to 3 mm) or thin rubber sheets, for the measurement of their physical or mechanical properties. The compositions thus obtained can also be extruded in the form of directly usable profiles, after cutting and / or assembly to the desired dimensions, for example as semi-finished products for tires. Table 2b

It should be noted that the compositions X, Y and Z based on the SBR / NR blend according to the invention have a higher Mooney "blend" value than those of the U, V and W compositions based on an unmodified SBR / NR blend. . As regards the dynamic properties, it will be noted that the Delta G * and tan (δ) max values of the compositions X, Y and Z according to the invention are lower than those of the compositions U, V and W based on an SBR blend. / NR not modified.

The hysteresis reduction of the SBR / NR-based cutting compositions according to the invention is related to the amount of NR modified according to the invention in the cutting, in other words, the decrease in hysteresis is more marked when the NR amount according to the invention is higher in the cutting. Example 3

CHARGE = MIX (SILICA / BLACK OF CARBON)

Each of these compositions has the following formulation (expressed in phr: parts per hundred parts of elastomer):

Table 3a

(1) = Natural rubber

(4) = N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine

(5) = coupling agent TESPT ("Si69" from Degussa)

(6) = CBS (Flexsys Santocure).

Each of the following compositions is carried out initially by thermomechanical work and then, in a second finishing time, by mechanical work. Is introduced successively, in a laboratory internal mixer type 'Banbury', whose capacity is 400 cm ³ , which is filled to 75% and whose initial temperature is about 70 ⁰ C, the elastomer, the black of carbon, 2/3 of the silica and the coupling agent. At 90 ^° C., the last third of the silica, stearic acid, 6PPD and paraffin. Zinc oxide is introduced at 140 ^° C.

The compositions thus obtained are then calendered, either in the form of plates (with a thickness ranging from 2 to 3 mm) or thin rubber sheets, for the measurement of their physical or mechanical properties.

Table 3b

It will be noted that the compositions AC and AD based on NR according to the invention have a higher Mooney "blend" value than those of the AA and AB compositions based on an unmodified NR. As regards the dynamic properties, it will be noted that the values of Delta G * and tan (δ) max of the compositions AC and AD according to the invention with varying amounts of silica and black in the composition are lower than those of the compositions AA and AB based on an unmodified NR.

Example 4: EXTENDED FORMULA

Each of these compositions has the following formulation (expressed in phr: parts per hundred parts of elastomer): Table 4a

(1) = natural rubber

(2) = "Zeosil 1165MP" silica from Rhodia (BET and CTAB: approximately 160 m ² / g)

(3) = coupling agent TESPT ("Si69" from Degussa) (4) = carbon black N234 (ASTM grade);

(5) = MES oil ("Catenex SNR" from Shell);

(6) = 1,2-cyclohexane dicarboxylate diisononyl ("Hexamoll DINCH" from BASF)

(7) = polylimonene resin ("Dercolyte Ll 20" from the company DRT)

(8) = diphenylguanidine (Perkacit DPG from Flexsys) (9) = N-1,3-dimethylbutyl-N-phenylparaphenylenediamine (Santoflex 6-PPD from the company)

Flexsys);

(10) = CBS (Flexsys Santocure)

Each of the following compositions is carried out initially by thermomechanical work and then, in a second finishing time, by mechanical work.

Is introduced successively, in a laboratory internal mixer type 'Banbury', whose capacity is 400 cm, which is filled to 75% and whose initial temperature is about 70 ⁰ C, the elastomer, the black of carbon, 2/3 of the silica, the coupling agent and the DPG. About a minute later, the last third of the silica, stearic acid, 6PPD, wax, resin and MES oil (Cl composition) or 1,2-cyclohexane diisononyl dicarboxylate (composition C2). Zinc oxide is introduced after about 3 minutes of mixing. The thermomechanical working step is carried out for 3 to 5 minutes, until a maximum temperature of about 165 ° C. falls.

The aforementioned first thermomechanical work time is thus achieved, it being specified that the average speed of the pallets during this first time is 80 rpm. The mixture thus obtained is recovered, cooled and then, in an external mixer (homo-finisher), the sulfur and sulfenamide are added at 30 ^° C., mixing again for a period of 3 to 4 minutes (second time). aforementioned mechanical work).

Table 4b

It will be noted that the compositions AJ, AK and AL according to the invention have a higher Mooney "mixture" value than that of the AG composition based on an unmodified NR. As regards the dynamic properties, it will be noted that the values of Delta G * and tan (δ) max of the compositions AJ, AK and AL according to the invention are lower than those of the composition AG based on an unmodified NR. The elastomers L, M and N comprising an isophthalic or aliphatic dihydrazide according to the invention make it possible to improve the hysteretic properties with respect to the unmodified elastomer A in the composition Cl.

In other words, the compositions AJ, AK and AL according to the invention based on NR comprising an isophthalic dihydrazide or an adipic dihydrazide or a dodecanoic hydrazide have crosslinked rubber properties which are improved over those of the unmodified NR-based AG composition due to reduced hysteresis.

The compositions AQ, AS and AT which do not conform to the invention have Delta G * and tan (δ) max values higher than those of the AG composition based on an unmodified NR. The elastomers Q, S and T comprising a hydroxynaphthoic hydrazide or a propionic hydrazide or a benzhydrazide do not make it possible to improve the hysteretic properties with respect to the unmodified elastomer A.

It will be noted that the values of Delta G * and tan (δ) max of the composition AR not according to the invention are also lower than those of the AG composition based on an unmodified NR. However, the Delta G * and tan (δ) max values of the compositions AJ, AK and AL according to the invention are lower than those of the compositions AQ, AR, AS and AT based on an NR comprising a hydroxynaphthoic hydrazide or a hydroxy-naphthylhydrazone (BMH) or a propionic hydrazide or a benzhydrazide. In other words, the compositions AJ, AK and AL according to the invention have crosslinked rubber properties which are improved compared to those of compositions AQ, AR, AS and AT based on a NR comprising a hydroxynaphthoic hydrazide or a hydroxy-naphthylhydrazone (BMH) or a propionic hydrazide or a benzhydrazide.

Table 4c

It will be noted that the compositions AO and AP according to the invention have a Mooney value "mixture" greater than that of the AM composition based on an unmodified NR.

As regards the dynamic properties, it will be noted that the values of Delta G * and tan (δ) max of the compositions A0 and AP according to the invention are lower than those of the composition AM based on an unmodified NR. The O and P elastomers comprising a terephthalic or adipic dihydrazide according to the invention make it possible to improve the hysteretic properties with respect to the unmodified elastomer F.

In other words, the compositions AO and AP according to the NR-based invention comprising a terephthalic dihydrazide or an adipic dihydrazide have crosslinked rubber properties which are improved over those of the AM composition. unmodified NR due to reduced hysteresis in composition Cl.

Table 4d

It will be noted that the compositions AY and AZ according to the invention have a Mooney value "mixture" greater than that of the composition AX based on an unmodified NR. As regards the dynamic properties, it will be noted that the values of Delta G * and tan (δ) max of the compositions AY and AZ according to the invention are lower than those of the composition AX based on an unmodified NR. The elastomers K and M comprising a terephthalic or adipic dihydrazide according to the invention make it possible to improve the hysteretic properties with respect to the unmodified elastomer A.

In other words, the compositions AY and AZ according to the invention based on NR comprising a terephthalic dihydrazide or an adipic dihydrazide have crosslinked rubber properties which are improved over those of the AX composition. unmodified NR due to reduced hysteresis in composition C2.

Example 5

MODE OF INTRODUCTION OF DIHYDRAZIDE

Each of these compositions has the following formulation (expressed in phr: parts per hundred parts of elastomer): Table 5a

(1) = Natural rubber

(2) = terephthalic dihydrazide

(3) = Rhodia Zeosil 1165MP Silica (BET and CTAB: approximately 160 m ² / g)

(4) = carbon black N330

(5) = N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine

(6) = coupling agent TESPT ("Si69" from Degussa)

(7) = CBS (Flexsys Santocure).

Each of the following compositions is carried out initially by thermomechanical work and then, in a second finishing time, by mechanical work. Is introduced successively, in a laboratory internal mixer type 'Banbury', whose capacity is 400 cm, which is filled to 75% and whose initial temperature is about 50 ⁰ C, the elastomer and the terephthalic dihydrazide (for the composition BA), the carbon black, 2/3 of the silica and the coupling agent. At 90 ^° C., the last third of the silica, stearic acid, 6PPD and paraffin. Zinc oxide is introduced at 140 ^° C.

The aforementioned first thermomechanical work time is thus achieved, it being specified that the average speed of the pallets during this first time is 70 rpm.

The mixture thus obtained is recovered, cooled and then, in an external mixer (homo-finisher), the sulfur and sulfenamide are added at 30 ^° C., mixing again for a period of 3 to 4 minutes (second time). aforementioned mechanical work).

The compositions thus obtained can also be extruded in the form of directly usable profiles, after cutting and / or assembly to the desired dimensions, for example as semi-finished products for tires.

Table 5b

It will be noted that the compositions K and BA according to the invention have a Mooney value "mixture" greater than that of the composition A based on an unmodified NR. As regards the dynamic properties, it will be noted that the values of Delta G * and tan (δ) max of the compositions K and BA according to the invention are lower than those of the composition A based on an unmodified NR. K elastomers comprising a terephthalic dihydrazide and A with the introduction of terephthalic dihydrazide into the mixer according to the invention makes it possible to improve the hysteretic properties with respect to the unmodified elastomer A.

In other words, the compositions K and BA according to the NR-based invention comprising a terephthalic dihydrazide have crosslinked rubber properties which are improved over those of the unmodified NR composition A due to a reduced hysteresis (i) when the molecule is introduced into the NR before mixing (making a masterbatch on a tool) and (ii) when the molecule is introduced into the mixer during mixing .

Example 6

EFFECT OF DIHYDRAZIDE RATE

Table 6a

(1) = Natural rubber

(2) = Rhodia Zeosil 1165MP Silica (BET and CTAB: approximately 160 m ² / g)

(3) = carbon black N330

(4) = N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine

(5) = coupling agent TESPT ("Si69" from Degussa)

(6) = CBS (Flexsys Santocure).

The method of incorporation of the molecule is as follows: On a roll tool (roll temperature regulated at 23 ^° C.), the rollers of which have a diameter equal to 150 mm, a gap of 2 mm and a rotation speed of the rolls of 20 rpm. natural rubber undergoes the following steps:

3) making 12 passes so as to disperse the powder and homogenize the sample

Each of the following compositions is carried out initially by thermomechanical work and then, in a second finishing time, by mechanical work. Is introduced successively, in a laboratory internal mixer type 'Banbury', whose capacity is 400 cm ³ , which is filled to 75% and whose initial temperature is about 50 ⁰ C, the elastomer, the black of carbon, 2/3 of the silica and the coupling agent. At 90 ^° C., the last third of the silica, stearic acid, 6PPD and paraffin. The zinc oxide is introduced at 140 ^° C. The thermomechanical working step is carried out for 3 to 5 minutes, until a maximum temperature of about 165 ° C. falls.

The compositions thus obtained can also be extruded in the form of directly usable profiles, after cutting and / or assembly to the desired dimensions, for example as semi-finished products for tires. Table 6b

It will be noted that the compositions BB and BC according to the invention have a Mooney value "mixture" greater than that of the composition A based on an unmodified NR.

As regards the dynamic properties, it will be noted that the values of Delta G * and tan (δ) max of the compositions BB and BC according to the invention are lower than those of the composition A based on a

NR not modified. The elastomers U and V comprising an adipic dihydrazide at different levels according to the invention make it possible to improve the hysteretic properties with respect to the unmodified elastomer A.

In other words, the compositions BB and BC according to the NR-based invention comprising an adipic dihydrazide at different levels have crosslinked rubber properties which are improved over those of the composition A based on NR unmodified due to reduced hysteresis.

Claims

1. Reinforced rubber composition based on at least (a) an elastomeric matrix comprising natural rubber, (b) a reinforcing filler of which at least 50% by weight of the total weight of the reinforcing filler consists of a inorganic filler, (c) a coupling agent and (d) a dihydrazide compound having the following formula I:

O O

H ₂ NHNC - R _n - CNHNH ₂

2. A rubber composition according to claim 1, characterized in that the dihydrazide compound is present in a proportion ranging from 0.25 to 7 phr.

3. rubber composition according to claim 1 or 2, characterized in that the weight fraction of the natural rubber in the elastomeric matrix is greater than or equal to 50% by weight of the total weight of the matrix.

4. A rubber composition according to claim 3, characterized in that the elastomeric matrix is made of 100% natural rubber.

5. rubber composition according to any one of claims 1 to 4, characterized in that the reinforcing filler comprises a reinforcing inorganic filler in proportions ranging from 55 to 95% by weight of the total weight of the filler.

Rubber composition according to one of Claims 1 to 5, characterized in that the inorganic filler is a silica.

Rubber composition according to any one of claims 1 to 6, characterized in that the dihydrazide compound is chosen from phthalic dihydrazide, isophthalic dihydrazide, terephthalic dihydrazide, dihydrazide succinic, adipic dihydrazide, azelaic dihydrazide, sebacic dihydride, oxalic dihydrazide, dodecanoic dihydrazide.

A process for preparing a reinforced rubber composition as described in any one of claims 1 to 7, comprising the steps of:

(i) the production, at a maximum temperature of between 130 ^° C. and 200 ^° C.

⁰ C, a first thermomechanical working time of the necessary basic constituents of the rubber composition, with the exception of the crosslinking system and optionally of an adhesion promoter, by incorporation in an intimate manner, by mixing , to the elastomeric matrix based on natural rubber, ingredients of the composition, then

(ii) the production, at a temperature below said maximum temperature of said first time, preferably less than 120 ^° C., of a second mechanical working time during which said crosslinking system and, where appropriate, the promoter of said crosslinking system are incorporated. adhesion, characterized in that, prior to carrying out step (i) above, the method comprises the steps of the manufacture of natural rubber comprising a step of adding the dihydrazide compound of formula I.

9. A method for preparing a component of the tire as described in any one of claims 1 to 7, comprising the following steps: (i) the realization, at a maximum temperature between 130 ⁰ C and 200

⁰ C, a first thermomechanical working time (sometimes called a "non-productive" phase) of the necessary basic constituents of the rubber composition, with the exception of the crosslinking system and optionally a promoter of adhesion, by intimately incorporating, by kneading, with the elastomeric matrix based on natural rubber, ingredients of the composition, then

(ii) the production, at a temperature below said maximum temperature of said first time, preferably below 120 ^° C., of a second mechanical working time during which said crosslinking system and, where appropriate, the promoter are incorporated; adhesion, characterized in that, prior to carrying out step (i) above, the method comprises a step of preparing a masterbatch based on natural rubber and the dihydrazide compound of formula I.

A method of preparing a tire component as described in any one of claims 1 to 7, comprising the steps of: (i) the production, at a maximum temperature of between 130 ^° C. and 200 ^° C.

⁰ C, a first thermomechanical working time (sometimes called a "non-productive" phase) of the necessary basic constituents of the rubber composition, with the exception of the crosslinking system and optionally a promoter of adhesion, by intimate incorporation, by mixing, with the elastomeric matrix based on natural rubber, ingredients of the composition, then

(ii) the production, at a temperature below said maximum temperature of said first time, preferably less than 120 ^° C., of a second mechanical working time during which said crosslinking system and, where appropriate, the promoter of said crosslinking system are incorporated. adhesion, characterized in that the dihydrazide compound of formula I is added to the mixture in step (i).

11. Semi-finished product rubber for tire, characterized in that it comprises a crosslinkable or crosslinked rubber composition according to any one of claims 1 to 7.

12. Semi-finished product according to claim 11, characterized in that said product is a tread.

13. Semi-finished product according to claim 11, characterized in that said product is an internal composition.

14. Pneumatic tire, characterized in that it comprises a semi-finished product according to one of claims 11 to 13